feat: simplify ABNF for v0.1 and introduce section in main document

[DecimalTurn]

This PR:

• Simplifies the ABNF diagram
  • No longer include mentions of LS (Line Seperator) and PS (Paragraph Seperator)
• Makes sure the ABNF is self-contained (no longer need to refer to core rules from RFC 5234.
• Makes the railroad diagram more similar with the style of ECMA railroad diagrams
• Makes the railroad diagram easier to read by re-ordering elements to make them closer to where they are needed and put the ones that are obvious at the end to save space in the core of the page.